Effects Of Chlorine And Ozone Disinfection Technology On Municipal Wastewater Quality

Wastewater reclamation could not only lighten water pollution degree but also resolve water shortage. The key problem is how to guarantee the water quality safety of the reclaimed water. Disinfection can eliminate the pathogenic microorganisms, prevent the popular disease's dissemination.It's an essential link in the wastewater reclamation treating processes. But disinfection might be form harmful by-products and cause some toxicity risk.In order to analyze the security of the disinfection technology,we use umu genotoxicity as the index for biotoxicity evaluation.The paper uses chlorine, ozone and two combinations disinfection to disinfect the recycled water of one municipal wastewater plant separately.We use conventional chemistry and biological toxic factors to evaluate the effects of different disinfection processing.The results are summarized as follows.1,The removal the TOC and chroma is not obvious from the water by chlorine disinfection, The concentration of UV254 increases along with the chlorine dosage increasing,while the concentration of ammonia nitrogen(NH3-N) decrease.. The removal efficiency of total E.coli by chlorine disinfection is good,and it increases along wirh the chlorine dosage and contact time.When the chlorine dosage and contact time rising,the production of THMs and HAAs largely increase.Along with the concentration of NH3-N increasing in wastewater, the production of THMs drops ,but HAAs'production have no obvious change.The recycled water has a high genotoxicity.After chlorine disinfection,the genotoxicity decreases with a low NH3-N concentration,but it increases notably with a high NH3-N concentration in wastewater.2,The ozone disinfection has an obviously efficiency in wastewater.The removal of TOC,UV254 and chroma is good.The removal efficiency of total E.coli by ozone disinfection is very good,.it increases along wirh the ozone dosage.Ozone can remove the total E.coli effectively with the low concentration.After ozone disinfection,the genotoxicity decreases gradually.The decrease is positively correlated with ozone dosage.3,The ozone oxidation can cause type transformation and the production quantity change of the typical by-products in the following chlorine disinfection.The concentration of THMs and HAAs correlate with chlorine dosage during pre-ozone with chlorine disinfection, in the low dose (5ppm), the concentration of THMs and the HAAs increases slowly along with the increasing of ozone concentration;But in the high dose (10ppm),the concentration of THMs and the HAAs reduces first and then increases along with the increasing of ozone concentration. Because wastewater contains bromine ion, the pre-ozone with chlorine disinfection would induce the increasing of bromo by-product.It can product more bromo THMs than HAAs.The ozone oxidation can reduce the genotoxicity greatly, and the following chlorine disinfection would reduce the genotoxicity slightly. On the whole,the genotoxicity of ozne-chlorine is small.